Thermal Testing

This is a study of a CRS Electronic’s luminaire device under various environmental conditions.

2. Test Parts

The testing proceeded in 3 parts. The first part was a 1000 hour test which cycled temperature between -55°C and 105°C while turning the power to the light fixture off and on again. The second part was a 24-hour high temperature soak, where the device was kept at the temperature of 107°C, and while the power to the device was turned off for 2 hours and then turned back on for two hours, and repeated until test conclusion. The final test was identical to the second test, excepting that the temperature was set to -55°C.

3. Test Results

3.1. CRS Electronics Part 1A Testing

3.1.1 Scope

This report is to detail CRS Electronics’ temperature part A testing on the luminaire device. The device was tested for 1000 hours.

Design temperature sweep: -55°C to +105°C, 1000 hours.

3.1.2 Notes About the execution of the Part 1A Test

1. After approx 2 days, the temperature sweep was widened to: -57°C to +107°C in order to ensure that the fixture reaches its target temperatures.

2. After resetting the temperature sweep (after day 2), a single setting was improperly programmed on the current meter. This is why it looks as though there was no current flowing through the device for the period between hours 46 and 70. Once this was noted, the setting was corrected. It should be emphasized that this was only a setting error, and that there was current flowing to the device, as evidenced by visually noting the presence of light coming from the thermal chamber.

3. The system was checked each business day to ensure that proper program execution was occurring. Once the system had finished its 1000 hour program, the fixture was allowed to return to room temperature, and was then inspected, and images of the fixture collected.

3.1.3 Main Outcomes from Part 1A Testing

1. The fixture physically survives the testing, and is capable of operation after the test.l

2. There is evidence of time-dependent performance change throughout the testing, which may be attributable to the temperature cycling, but which may also be natural device ageing.

3. Current draw at +107°C is changing over time, and ranges from approx. 2.43 A (@11.67 V) at the start of test, to approx. 2.45 A (@11.67 V) at the end of the test. This shift is highlighted by red bars overlaid on the data plot shown in figure 1.

4. Current draw at -57°C is changing over time, and ranges from approx. 2.3 A (@11.67 V) at the start of test, to approx. 2.0 A (@11.67 V) at the end of the test. This shift is highlighted by blue bars overlaid on the data plot shown in figure 1.

5. Maximum current draw is 2.95 A at an unknown temperature (@11.67 V).

3.1.4 Detailed Results Information

Figure 1. shows the temperature and current data plotted against time. The trend bars that have been added show time-dependent features of the plot (see points 3 & 4 in “Main Outcome from Testing”). In contrast to the preliminary report, the stable current draw at the low temperature extreme (-57°C) is lower than the stable current draw at the high temperature extreme (107°C); at an unknown temperature between these two extremes, the light fixtures draws a maximum current of approx. 2.95 amps. Figure 2 shows a close-up image of the current and temperature over a reduced time period to highlight important characteristics in the current-temperature relationship. This is a brief description of a single temperature/current period on Figure 2. The numbers correspond to the red numbers on Figure 2.

Power is reactivated after being off at high temperature. An immediately measured current is seen which is changing over time. The current quickly stabilizes at a value of approx. 2.44 A, but as the system starts to heat up due to excess power dissipation, the current lowers by approx 0.01A.

The temperature falls from 107°C down to -57°C. The UUT will thermally lag the chamber ambient temperature, but as temperature falls the current rises. It would seem that there is a peak current which occurs at a temperature somewhere within the operating region (i.e. not at one of the two extreme temps).

The ambient temperature reaches the low value and stabilizes. After 30 minutes, the power shuts off, and the current falls to zero. When the power is reactivated at low temperature, there is an immediately measured current which is changing over time. The measured current quickly tends towards 2.22 A, the approx. stable current at -57°C. The short section of increasing current which is concave down is likely being caused by the temperature increase due to the power dissipation after the unit has been re-energized.

The ambient in the chamber then begins to rise back towards 107°C. The UUT also begins to increase in temperature, and the current subsequently increases until it passes the temperature at which current is maximized (max current is approx 2.94 A, unknown maximizing temperature) and then begins to decrease again. The current drops to a value of approx 2.45 A, which is close to its stable operating current at 107°C.

The power to the unit is then shut off, and the device stabilizes in temperature.

Cycle complete, and repeats.

Figure 1. Current Vs time. The trend bars highlight timedependent
features of the current data.

Figure 2. Close-up view of Current and temperature vs time.

Figure 3. Picture taken of unit while at room temperature after 1000 hour testing. Visual inspection of the DUT reveals no apparent physical degradation. The discoloration on the metal in picture is from tape residue. We affixed a thermocouple to the fixture for part of the test.

Figure 4. Picture taken of the unit power cable after testing. The originally coloured yellow portion was outside of the thermal chamber during the test, while the brown part was inside the chamber.

3.2. CRS Electronics Part 1B Testing

3.2.1 Scope

The report on part 1B of the CRS Electronics Temperature testing is meant to document the method of testing, and aberrations from the testing designs, and report on the main results of the testing.

3.2.2 Notes About the execution of the Part 1B Test

1. The program was designed to maintain a constant temperature of 107°C, while alternatively halting power, and then flowing power for 2-hour time periods.

3.2.3 Main Outcomes from Part 1B Testing

1. The fixture worked properly throughout the test, and was capable of proper operation after the test had concluded.

2. No apparent ageing effects were visible

3.2.4 Detailed Results Information

Figure 5 shows a plot of the current and temperature data which has been overlaid. The blue curve represents the temperature, and it is apparent that for the first 2 hours of the test, the temperature increases from room temperature up to 107°C. The temperature is maintained at this level until the remainder of the 24 hours have elapsed and then the temperature begins to naturally decrease towards room temperature. The current curve, in green, decreases as the temperature is increased, and is off for the period of 3.2- 5.2 hours. Power to the device is then reapplied. The device will have stabilized at the ambient of 107°C, and the current required for this temperature is 2.46 amps. As the device dissipates power, it increases in temperature until stabilizing, with a stable current of 2.44 amps. The process is repeated until the test concludes.

Figure 5. A plot of UUT current and temperature data collected vs time during the CRS Electronics part 1B test.

Figure 6. Front view of the device after part 1B testing. No obvious problems
were noted.

3.3. CRS Electronics Part 1C Testing

3.3.1 Scope

The report on part 1C of the CRS Electronics Temperature testing is meant to document the method of testing, and aberrations from the testing designs, and report on the main results of the testing.

3.3.2 Notes About the execution of the Part 1B Test

1. The program was designed to maintain a constant temperature of -57°C, while alternatively halting power, and then flowing power for 2-hour time periods.

3.3.3 Main Outcomes from Part 1C Testing

1. The fixture worked properly throughout the test, and was capable of proper operation after the test had concluded.

3.3.4 Detailed Results Information

Figure 7 shows a plot of the collected temperature and device current data against time. The temperature curve is seen to decrease to -57°C, and to hold this temperature until the end of the test. The temperature is then allowed to naturally come back to room temperature. The current increases as the temperature decreases until it reaches a maximum value, and then begins decreasing as the temperature decreases. The power is turned off between hours 3.1 and 5.1, and during this time, the fixture will thermally stabilize at -55°C. When the power is re-applied, then unit begins to create its own heat, and the unit will increase in temperature. The current increases as this occurs. And then stabilizes at the device reaches a stable temperature within the thermal chamber. This stable current, however, seems to decrease over the course of the experiment, beginning at 2.18 amps, and ending at approx. 2.08 amps. This may indicate a form of ageing is occurring, though it is unknown whether it is due to the exposure to an extreme environment, or whether it is a natural form of burn-in ageing.

Figure 7. A plot of UUT current and temperature data collected vs time during the CRS Electronics part 1C test.

Figure 6. Front view of the device after part 1B testing. No obvious problems
were noted.